Hydrocarbylphenyl diaminodithiol radionuclide complexes and their use in imaging

ABSTRACT

An agent for imaging organs using a radioactive complex of a radioactive metal with a benzene ring having two 2-mercapto-2-methylpropylamino substituents where one of these mercapto substituents is substituted with a hydrocarbyl group.

This is a division of application Ser. No. 07/576,163, now U.S. Pat. No.5,026,913 filed Aug. 30, 1990 which is a continuation of applicationSer. No. 07/445,212 filed Dec. 12, 1989, abandoned.

SUMMARY OF THE INVENTION

In accordance with this invention, we have discovered that radionuclidecomplexes of a compound of the formula: ##STR1## wherein R₁, R₂, R₃ andR₄ are halogen, hydrogen or lower alkyl, with at least one of R₃ and R₄being hydrogen; and one of R₅ and R₅ ' being hydrogen whereas the otherof said R₅ and R₅ ' being alkyl containing from 1 to 10 carbon atoms,alkenyl containing 2 to 10 carbon atoms, alkynyl containing from 2 to 10carbon atoms or lower alkylcycloloweralkyl;

or pharmaceutically acceptable salt thereof; are useful for imagingvarious organs of the body such as the brain, heart, kidney and liver.The compounds of formula I and their salts demonstrate rapidaccumulation in various organs and have the ability to penetrate the"blood/brain barrier".

In contrast to brian perfusion agents such as described in J. Nucl. Med.26:P105 (1985) and Baldas, J. C.S. Dalton, 1981 1798 and Kung, J. Nucl.Med. 25:326-332, 1984 which are technetium-99m complexes ofdiaminodithiols having the following formula: ##STR2## where R₁ ', R₂ 'and R₄ ' are hydrogen or lower alkyl. The compounds of formula I andtheir pharmaceutically acceptable salts have greater uptake in variousorgans of the body, in particular the brain. Also the compounds offormula I and their salts have a greater ability to penetrate theblood/brain barrier and demonstrate rapid localization of theradioactivity following intravenous administration. These propertiesmake the compounds of formula I above and their pharmaceuticallyacceptable salts suitable as in vivo imaging agents for diagnosingdiseases and disorders of various organs such as the brain.

DETAILED DESCRIPTION

As used throughout this application, the term "lower alkyl" includesboth straight chain and branched chain saturated aliphatic hydrocarbongroups containing from 1 to 7 carbon atoms said methyl, ethyl, propyl,isopropyl, butyl and isobutyl, etc. The term alkenyl designates bothstraight and branched chain aliphatic hydrocarbon groups containing from2 to 10 carbon atoms and having an olefinic double bond, such as vinyl,allyl, prop-2-en-1-yl, etc. The term alkynyl designates both straightand branched chain aliphatic hydrocarbon groups containing from 2 to 10carbon atoms and having an acetylenic triple bond, such as propargyl.The term cycloloweralkyl designates cycloaliphatic saturated hydrocarbongroups containing from 3 to 6 carbon atoms such as cyclopropyl,cyclobutyl and cyclohexyl. The term lower alkylcycloloweralkyldesignates lower alkylcycloloweralkyl groups connected to the thio groupon the compound of formula I via the lower alkyl substituent whereinlower alkyl and cycloloweralkyl are defined above.

As further used herein, the term "halogen" or "halo", unless otherwisestated, comprehends all halogens such as fluorine, chlorine, bromine andiodine. Alkali metal includes all alkali metal such as lithium, sodiumand potassium.

As also used herein, the term "aryl" signifies both monovalentmononuclear aromatic hydrocarbon groups such as phenyl and monovalentpolynuclear aryl groups such as naphthyl, anthryl, phenanthryl, etc. Thepreferred aryl groups are the phenyl, naphthyl and anthryl. The termarylene designates the divalent aromatic hydrocarbon groups such asphenylene, naphthalene, etc.

The term "aryl, lower alkyl" designates aryl lower alkyl substituentswhere aryl and lower alkyl groups are defined above, particularlybenzyl.

The term "lower alkanoyl" as used throughout this specificationdesignates "lower alkanoyl" groups containing from 2 to 7 carbon atomssuch as acetyl, propionyl, etc. The term "arylloweralkanoyl" designatesmonovalent arylloweralkanoyl groups where aryl and lower alkanoyl aredefined as above with phenylacetyl being preferred. The term "aroyl"defines aroyl groups where the aryl group is defined as above withbenzoyl being preferred.

As used herein, the term "thiol protecting group" includes all of theconventional groups which are commonly employed to protect the thiolmoiety. Among these groups are included lower alkylaminocarbonyl such asethylaminocarbonyl, loweralkanoylaminomethyl, aroylaminomethyl,triarylmethyl such as triphenylmethyl, aroyl such as benzoyl,aryloxycarbonyl such as phenoxycarbonyl, arylloweralkoxylcarbonyl,preferably arylmethoxycarbonyl such as benzyloxycarbonyl, loweralkoxycarbonyl such as t-butoxycarbonyl. Among the preferred loweralkanoylaminomethyl groups is acetamidomethyl and among the preferredaroylaminomethyl is benzoylaminomethyl. The thiol protecting groups areremovable by treatment with heavy metallic ions such as mercuric ions,technetium ions, silver ions, as well as any of the radioactive metalswhich form the complex. Any of the conventional methods commonlyemployed in removing these thiol protecting groups can be utilized inaccordance with this invention.

In accordance with one preferred embodiment, R₁, R₂ and R₃ are hydrogen.When one of R₅ and R₅ ' are alkyl, the preferred alkyl group has theformula: ##STR3## wherein n is an integer of from 0 to 5, and R₆ is H or--CH₃.

When one of R₅ and R₅ ' is an alkenyl group, preferably the group hasonly one olefenic double bond and most preferably has the formula:##STR4## wherein R₇ is hydrogen or --CH₃ ; R₆ is as above; x is aninteger from 0 to 3; z is an integer from 0 to 1 and y is an integerfrom 0 to 2

When one of R₅ and R₅ ' is an alkynyl group, the group preferably hasonly one acetylenic triple bond and most preferably has the formula:##STR5## where R₆, x and y are as above.

When one of R₅ and R₅ ' is cycloalkylloweralkyl, preferably the grouphas the formula: ##STR6## wherein n and R₆ are as above and p is aninteger from 0 to 3.

The radionuclide for use in this invention can be any radioactive metalcapable of pharmaceutical administration. Among the radioactive metalsare included radioactive isotopes of indium, technetium, ruthenium orgallium. Among the radioactive isotopes are included indium-111,indium-113m, indium-114m, technetium-99m, ruthenium-97 and gallium-67,with technetium-99m being especially preferred.

The compound of formula I as well as the complex formed from thecompound of formula I may form acid addition salts due to the presenceof the amine functional groups. Any conventional acid addition saltcapable of intravenous administration can be utilized in accordance withthis invention. Among the suitable acids which can be utilized to formthe salts of the complex formed from the compound of formula I includeinorganic acids such as hydrochloric acid, hydrobromic acid, sulfuricacid, and the like.

In accordance with one embodiment of this invention, the compound offormula I is formed by reacting a compound of the formula ##STR7## witha compound of the formula: ##STR8## wherein R₁, R₂, R₃, R₄ are as above;and R₁₅ is alkyl containing from 1 to 10 carbon atoms, alkenylcontaining, from 2 to 10 carbon atoms or alkynyl containing from 2 to 10carbon atoms, or lower alkylcycloloweralkyl.

In the condensation of the compound of the formula III with a compoundof formula IV to produce the compound of formula I, any conventionalmethod of condensing an aldehyde with a primary amine can be utilized.Among the preferred methods for carrying out this condensation is bycondensing the aldehyde with the amine in the presence of an organicacid such as a lower alkanoic acid to produce a Shiff Base, andthereafter reducing the Shiff Base with a hydride reducing agent. Anyconventional hydride reducing agent can be utilized to carry out thisreaction, with the preferred reducing agents being lithium aluminiumhydride and sodium cyanoborohydride. This reaction can be carried out inan inert organic solvent. Furthermore, this reaction can be carried outwithout the presence of the organic acid. However, for best results itis preferable that acid be present. Furthermore, the reaction can becarried out by simply mixing the compound of formula III with thecompound of formula IV in an inert organic solvent medium containing thehydride reducing agent. In carrying out this reaction any conventionalinert organic solvent can be utilized. Furthermore, temperatures andpressures are not critical and this reaction can be carried out at roomtemperature and atmospheric pressure. On the other hand, if desired,elevated or reduced temperatures can be utilized.

The compound of formula III can be prepared by reactingo-phenylenediamine with isobutylene sulfide in accordance with theprocedure disclosed in Synder, et al., J. Am. Chem. Soc. 69:2672-274(1974). This reaction can be carried out by heating o-phenylenediamineand isobutylene sulfide in a closed system such as a bomb totemperatures greater than the boiling point of isobutylene sulfide. Inaccordance with this process, the corresponding compound of formula IIIwhere both amino groups are substituted with a 2-mercapto-2-methylpropyl substituent (XI) is formed in a small amount. This disubstitutedcompound can be removed from the compound of formula III by conventionalmeans such as extraction or crystalization.

The compound of formula IV can be prepared from the dialdehyde of theformula: ##STR9## when R₈ is a protected carbonyl group.

In compound formula V, R₈ can be any protected carbonyl group such as anacetal protected carbonyl. The term protected carbonyl group refers to agroup which may be hydrolyzed to regenerate a carbonyl group underconventional hydrolysis conditions. These groups include those formedwhen the carbonyl is protected as a di(loweralkyl)-acetal, an alkyleneacetal or an arylene acetal. Example of di(loweralkyl)-acetals aredimethyl acetals, diethyl acetals, etc. Alkylene acetals are derivedfrom 1,2 or 1,3-glycols, such as ehtylene glycol, 1,3-propylene glycol,2,3-butylene glycol, etc. Arylene acetals are derived from catecholssuch as phenylene-1,2-diols, alkyl-phenylene-1,2-diols,naphthalene-1,2-or-2,3-diols. The compound of formula V is derived fromthe corresponding compound where R₈ is a carbonyl group by conventionaltreatment to form the desired acetal.

The compound of formula V is converted to the compound of formula IV viathe following intermediates ##STR10## wherein R₈ and R₁₅ are as above.

In converting the compound of formula V to the compound of formula VI,the compound of formula V is reduced in an anhydrous medium. In thisrespect, any conventional method of anhydrous reduction can be used tocarry out this conversion. Generally, it is preferred to carry out thisreduction by treating the Compound V with an alkali metal such as sodiummetal in liquid ammonia. In carrying out this reaction, the temperaturebelow the boiling point of liquid ammonia is utilized.

The compound of formula VI can be converted to the compound of formulaVII by reacting the compound of formula VI with a halide of the formula:

    R.sub.15 X                                                 VIII

wherein R₁₅ is as above; and

X is a halogen.

Among the preferred compounds of formula VIII are compounds of theformula: ##STR11## wherein X, n and R₆ are as above, ##STR12## whereinX, R₆, R₇, x, y and z are as above, ##STR13## wherein R₆, X, x and y areas above, ##STR14## wherein X, n, p and R₆ are as above. In reacting thecompound of formula VI with the halide of formula VIII, any conventionalmethod for condensing a thiol with an organic halide can be used to formthe compound of formula VII. Among the preferred methods is to condensethe compound of formula VI with the compound of formula VIII in thepresence of a base. Any conventional base can be utilized in thisreaction. Among the preferred bases are the alkali metal hydrides,alkali metal hydroxides or alkali metal carbonates. Generally thisreaction is carried out in an inert organic solvent medium. Anyconventional inert organic solvent can be used as the reaction mediumwith ethers such as tetrahydrofuran as well as lower alkanols such asmethanol being especially preferred. If a lower alkanol is used as theorganic solvent, the solvent may also contain water. In carrying outthis reaction of the compound of formula VII with a halide, temperatureand pressure are not critical and this reaction can be carried out atroom temperature and atmospheric pressure. If desired, higher or lowertemperatures can be utilized.

The compound of formula VII can be converted to the compound of formulaIV by acid hydrolysis in an aqueous medium. Any conventional method ofhydrolyzing a ketal into the corresponding carbonyl group can be used inthis conversion.

In accordance with another embodiment, the compound of formula I can beprepared from o-phenylenediamine via the following intermediates:##STR15## wherein R₁, R₂, R₃ and R₄ are as above.

The reaction of o-phenylenediamine to produce the compound of formula Xis carried by reacting o-phenylene diamine with the precursor of thecompound of V, i.e. the compound of formula V where both are R₈ groupsare carbonyl and not protected carbonyl groups. This reaction is carriedout in the same manner hereinbefore described in connection with thereaction of the compound of formula III with the compound of IV toproduce the compound of formula I.

The compound of formula X is converted to the compound of formula XI byreduction in an anhydrous medium. This reaction is carried out in thesame manner as hereinbefore described in connection with the conversionof the compound of formula V to the compound VI. In producing thecompound of formula I from the compound of formula X, the compound offormula XI is reacted with the compound of formula VIII in the samemanner as described in connection with the reaction of the compound offormula VI with the compound of formula VIII to produce the compound offormula VII. Depending upon which R₁₅ group is desired, a compound offormula VIII-A, VIII-B, VIII-C or VIII-D can be utilized in thisreaction. In this reaction, corresponding compound of formula I isformed with both thio group substituted with R₁₅. However, thisdisubstituted thio compound forms in only a small amount and may beseparated from the compound of formula I by conventional separationmethods such column chromatography.

In accordance with this invention the compound of formula I can beprepared by reacting the compound of formula X with a Gringnard or alkyllithium form of the compound of formula VIII-B where x and z are O. Thisreaction is carried out by conventional means to produce the compound offormula I where 1 of R₅ or R₅ ' is ##STR16## where R₇ and y are asabove.

In accordance with another embodiment of this invention, the compound offormula I can be prepared from the compound of formula III via thefollowing intermediate: ##STR17## wherein R₁, R₂, R₃, R₄, R₅ and R₅ 'are as above.

In forming the compound of formula XII, the compound of formula III isreacted with a compound of the formula ##STR18## wherein R₁₅ is asabove.

The compound of formula III is reacted with the compound of formula XIIIto form the amide of formula XII. Any conventional method of condensingan amine with a carboxylic acid to form an amide, can be utilized tocarry out this reaction. Generally, this amine condensation with an acidcan be carried out by reacting the amine of formula III with a reactivederivative of an acid of formula XIII such as the halo derivative ofthis acid. Any conventional method of converting an acid into an acidchloride, such as by reacting the acid of formula XIII with thionylchloride, can be utilized in forming the acid halide of the compound offormula XIII. The reactive derivative of the compound of formula XIII iscondensed with the compound of formula III to prepare the compound offormula XII utilizing any conventional method of reacting an amine andan acid chloride to form an amide.

The compound of formula XII can be converted to the compound of formulaI by reduction with a hydride reducing agent. Any conventional hydridereducing agent can be utilized in this conversion. Among the preferredhydride reducing agents are lithium aluminum hydride. The use of ahydride reducing agent such as lithium aluminum hydride only reduces thecarbonyl group without affecting any double or triple bonds within themolecule of the compound of formula XII. Any of the conditionsconventional for hydride reduction can be used in carrying out thisreduction.

The compound of formula XIII is formed from a compound of the formula:##STR19## by condensing with the halide of formula VIII. Depending onthe particular R₁₅ substituent desired, a compound of formula VIII-A,VIII-B, VIII-C or VIII-D is be utilized in this condensation. Thiscondensation takes place in the same manner as described in connectionwith the condensation of the compound of formula VI with the compound offormula VIII to produce the compound of formula VII.

The complex which can be utilized in imaging organs particularly thebrain is formed by reacting the compound of formula I with the salt of aradioactive metal. Any conventional salt of the aforementionedradioactive metals can be utilized in forming the complex. If one wishesto form the radioactive technetium complex of the compound of formula I,one can react technetium-99m pertechnetate with the compound of formulaI in the presence of a reducing agent such as a stannous reducing agentparticularly stannous chloride. On the other hand, radiolabelling can becarried out with other conventional salts of radioactive metals such asindium, technetium, gallium and ruthenium. Among the other salts are theacetate, citrate and halide salts, such as the chloride, bromide,fluoride and iodide salts. The reaction to form the complex is carriedout by simply mixing radioactive metal salts with a compound of formulaI. This reaction can be carried out in a solvent medium preferably anaqueous media at room temperature. In carrying out this reaction,temperature and pressure are not critical. Thus reaction can be carriedout at room temperature and atmospheric pressure.

The complexes formed by reacting the compound of formula I, withtechnetium-99m pertechnetate and a reducing agent such as stannouschloride has the following formula ##STR20## where R₁, R₂, R₃, R₄, andR₁₅ are as above.

The radioactive metal complex prepared from the compound of formula Imay be administered intravenously in any conventional medium byintravenous injection, such as an aqueous saline medium, or in a bloodplasma medium. Such medium may also contain conventional pharmaceuticaladjuvant materials such as, for example, pharmaceutically acceptablesalts to adjust the osmotic pressure, buffers, preservatives and thelike. Among the preferred mediums are plasma and normal salinecontaining a solubilizer suitable for intravenous injection such as2-hydroxypropyl-β-cyclodextrin.

Radiolabelling the compound of formula I to form the radioactive complexcan be carried out by conventional means sucha s described above. Theradioactive metal complex of this invention can be injectedintravenously into a patient for diagnostic imaging of all conventionalorgans of the body, i.e. lung, heart, liver, kidney, brain, etc. Inaccordance with this invention, the radioactive metal complex of formulaI is administered in a single unit injectable dose. Any of the commoncarriers, such as sterile saline solution, plasma, etc. can be used forpreparing the injectable solution for use to diagnostically image inaccordances with this invention. Generally, the unit dose to beadministered contains radioactivity of about 3.0 mCi to about 30 mCi,preferably 10 mCi to about 20 mCi. The solution to be injected is in aunit dosage form of about from 0.1 milliliters to about 10 milliliterspreferably from about 1 to about 5 milliliters. After intravenousadministration, the radioactive metal complex of formula I will imagethe organs in vivo. Any conventional method of visualizing or imagingfor diagnostic purposes can be utilized in accordance with thisinvention.

In accordance with this invention, the radioactive complex can bedistributed in a saline or plasma medium or the compound of formula Ican be utilized and the radioactive complex formed in situ prior toinjection by mixing the compound of formula I above with a radioactivemetal to form the complex just prior to administration. On the otherhand, a kit can be utilized which contains a certain quantity of thecompound of formula I and a suitable reducing agent such as stannouschloride, and a suitable solubilizer such as2-hydroxypropyl-β-cyclodextrin. In addition the kit may contain ascorbicacid for stabilizing the complex once it is formed and a correspondingquantity of a salt of a radioactive material for forming the complex insitu prior to injection. On the other hand this radioactive salt can beindependently furnished to the hospital or radiopharmacy.

The invention is further illustrated by the following examples, whichare not intended to limit the invention.

EXAMPLE 1 2-Amino-1-(2-mercapto-2-methylpropylamino)benzene

o-Phenylenediamine (15.31 g, 1.42×10⁻¹ mol, 100 M%) and 12.46 g(1.42×10⁻¹ mol, 100 M%) isobutylene sulfide (Synder et al, J. Am. Chem.Soc. 69: 2672-2674, 1947) were mixed in a Parr bomb and heated in anoven at 80° C. for 18 hr. The bomb was cooled to room temperature andthen opened. The crude brown oil contained some solid. The mixture wasdissolved in 150 ml ether (some white solid did not dissolve), washedwith saturated aqueous NaCl solution, and the solvent was removed on therotary evaporator. The oily residue was placed on flash silic in a 600ml sintered glass funnel and eluted with 500 ml portion of hexane, 90%hexane/ether, twice with 80% hexane/ether and twice with 50%hexane/ether. Evaporation of the first 50:50 hexane/ether fraction gave7.36 g (26.5%) of 2-amino-1-(2-mercapto-2-methylpropylamino)benzene as awaxy crystalline product, mp 38°-40° C.

EXAMPLE 22-(2-Mercapto-2-methylpropylamino)-1-[4-pentenylthio)-2-methylpropylamino]benzene

2-Amino-1-(2-mercapto-2-methylpropylamino)benzene (0.155 g, 7/9×10⁻⁴mol) and 0.30 g (1.74×10⁻³ mol, 220 M%) of2-(4-pentenylthio)-2-methylpropanal were dissolved in 40 ml methanol.Acetic acid (0.09 ml, 1.59×10⁻³ mol, 200 M%) was added followed by 0.155g (2.3×10⁻³ mol, 300 M%) sodium cyanoborohydride. The reaction wasstirred at room temperature under nitrogen for 17 hr, then 20 ml 0.5 MHCl was added and the mixture was extracted with 2×40 ml diethyl ether.The ether layer was washed with 30 ml saturated NaCl solution and dried(Na₂ SO₄), and the solvent was removed on the rotary evaporator. Theproduct was purified by radial chromatography on a 2 mm silica plateeluting with 50 ml 100% hexane and 100 ml 90% hexane/ether to give 0.27g (97% yield) of2-(2-mercapto-2-methylpropylamino)-1-[2-(4-pentenylthio)-2-methylpropylamino]-benzeneas an oil.

EXAMPLE 3 2,2'-Dithio-bis(2-methylpropanal)bis-ethylenedioxy acetal

2,2'-Dithio-bis(2-methylpropanal) (4.12 g, 2.00×10⁻² mol, 100 M%) andethylene glycol (5.00 ml, 8.97×10⁻² mol, 448 M%) were placed in a 250 mlround-bottom flask containing 30 ml benzene and 0.0463 g (2.43×10⁻⁴ mol,1.2 M%) p-toluenesulfonic acid monohydrate. The reaction flask wasequipped with a Dean-Stark trap and heated to reflux for 6 hours, whenthe theoretical amount of water had collected in the Dean-Stark trap.The reaction was stirred at 21° C. for 16 hr, then poured into 50 mldiethyl ether and washed with 30 ml 0.5 M NaOH. The ether layer waswashed with 20 ml saturated sodium chloride, dried over MgSO₄, filtered,and the solvent was removed on the rotary evaporator to afford 5.51 g2,2'-dithio-bis(2-methylpropanal)bis-ethylenedioxy acetal (94% yield).

EXAMPLE 4 2-Mercapto-2-methylpropanalethylenedioxy acetal

2,2-Dithio-bis (2-methylpropanal)bis-ethylenedioxy acetal, (2.40 g,8.16×10⁻³ mol, 100 M%) was placed in a 250 ml round-bottom flaskequipped with a dry ice/acetone cold finger. The reaction flask and coldfinger were cooled with dry ice and acetone. Ammonia gas was condensedby the cold finger and dripped into the reaction flask until 40 mlliquid ammonia was in the round-bottom flask. Small balls ofhexane-washed sodium metal were added one at time, causing the reactionmixture to turn blue. Tetrahydrofuran (20 ml) was added after 30 min tohelp dissolve the insoluble starting material. The blue solution rapidlybecame colorless upon addition of the freshly distilled tetrahydrofuran.The glassy starting material slowly dissolved as the sodium metal wasadded. After 3.5 hr all of the starting material was dissolved and thereaction solution remained blue when sodium was added. Solid ammoniumchloride was added, causing the reaction to change from blue tocolorless. The flask was then removed from the dry ice-acetone bath andplaced in a 40° C. warm water bath to evaporate the ammonia. The crudesolid reaction mixture was dissolved in 100 ml water and concentratedphosphoric acid was added until the solution was pH 2. The aqueoussolution was extracted with 2×100 ml diethyl ether. The ether layerswere combined, washed with 50 ml saturated sodium chloride, and driedover sodium sulfate. The solvent was removed on the rotary evaporate toobtain 2.34 g (97% yield) of 2-mercapto-2-methylpropanalethylenedioxyacetal as an oily product with a strong smell. TLC (1:1 ether/hexanes)Rf 0.66.

EXAMPLE 5 2-(4-pentenylthio)-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal (3 g, 2.0×10⁻² mol) wasdissolved in 50 ml tetrahydrofuran (freshly distilled over sodium).Sodium hydride (50% mineral oil dispersion washed with 3×5 ml portionsof hexane) (1.15 g, 2.42×10⁻² mol, 120 M%) was then added. The mixturewas stirred under nitrogen for 10 minutes, followed by the addition of2.62 ml, (2.43×10⁻² mol, 110 M%) 5-bromo-1-pentene. The mixture wasstirred under nitrogen for 18 hours, then 10 ml methanol was addedslowly, 100 ml H₂ O was added, and the mixture was extracted with 2×100ml diethyl ether. The combined ether extracts were washed with saturatedNaCl, dried over anhydrous Na₂ SO₄, and the solvent was removed on therotary evaporator to give 4.5 g (99% yield) of2-(4-pentenylthio)-2-methylpropanalethylenedioxy acetal as a yellow oil.

EXAMPLE 6 2-(4-Pentenylthio)-2-methylpropanal

2-(4-Pentenylthio)2-methylpropanalethylenedioxy acetal, (4.5 g,2.06×10⁻² mol) was dissolved in 25 ml tetrahydrofuran, then 25 ml 0.5 MHCl was added, and the mixture was heated to reflux for 3 hours. Thecooled reaction mixture was treated with 100 ml H₂ O, and the aqueouslayer was extracted with 2×100 ml portions of diethyl ether. Thecombined ether layers were washed with 100 ml saturated NaCl, and driedover anhydrous Na₂ SO₄. Rotary evaporation yielded 2.9 g (82% yield) of2-(4-opentenylthio)-2-methylpropanal as a yellow oil.

EXAMPLE 7 Tc-99m complex of2-(2-Mercapto-2-methylpropylamino)-1-[2-pentenylthio)-2-methylpropylamino]benzene.

2-(2-Mercapto-2-methylpropylamino)1-[2-(4-pentenylthio)-2-methylpropylamino]benzene(0.25-5 mg) was dissolved in 3 ml 50% ethanol/water containing 0.5-80mCi NaTcO₄ Tc-99m. Nitrogen gas was bubbled through the solution for 3minutes, then stannour chloride (0.001-0.2 ml, containing 1×10⁻⁸ to2.0×10⁻⁶ mol) was added to the solution to produce the Tc-99m complex of2-(2-mercapto-2-methylpropylamino)-1-[2-(4-pentenylthio)-2-methylpropylamino]benzene.The purity of the complex was then measured by TLC and HPLC. HPLC (9:1ethanol/H₂ O, 1.5 ml/min, Waters Radial-Pak (C18) Rt. 3.78 min,radiochemical purity 100%. TLC (ethyl acetate/methanol/water/15 M NH₄OH-86:10:3:1, Rf 0.92, radiochemical purity 97%. Electrophoresis (0.5 MNaH₂ PO₄, pH 4.5, 300 volts, 45 min) neutral.

EXAMPLE 8 2-(trans-2-Butenylthio)-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal, (2.15 g, 1.45×10⁻² mol,100 M%) was dissolved in 130 ml tetrahydrofuran. Hexane-washed sodiumhydride (50% in oil) 0.77 g (1.60×10⁻² mol, 110 M%) was added to thereaction solution. Crotyl bromide (1.64 ml, 1.60×10⁻² mol, 110 M%) wasadded to the reaction solution which was then stirred at 21° C. for 19hr before adding 60 ml H₂ O. The reaction mixture was extracted with2×60 ml ether. The organic extracts were combined, washed with 40 mlsaturated NaCl solution and dried with Na₂ SO₄. The ether was removed onthe rotary evaporator to afford 2.80 g (95% yield) of2-(trans-2-butenylthio)-2-methylpropanal-ethylenedioxy acetal as an oil.

EXAMPLE 9 2-(trans-2-Butenylthio)-2-methylpropanal

2-(trans-2-Butenylthio)-2-methylpropanalethylenedioxy acetal (2.56 g,1.27×10⁻² mol, 100 M%) was placed in a mixture of 40 ml tetrahydrofuranand 100 ml 0.5 M HCl. The solution was heated at reflux for 2 hr andthen extracted with 2×40 ml diethyl ether. The organic extracts werecombined, washed with 40 ml saturated aqueous NaCl solution, and dried(Na₂ SO₄). The solvent was removed on the rotary evaporator to afford1.94 g (96.7% yield) 2-(trans-2-butenylthio)-2-methylpropanal as an oil.

EXAMPLE 10

1-[2-(trans-2-Butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene

2-Amino-1-(2-mercapto-2-methylpropylamino)benzene (0.36 g, 1.84×10⁻³mol) and 0.58 g (3.67×10⁻³ mol, 200 M%)2-(trans-2-butenylthio)-2-methylpropanal were reacted by the proceduresin Example 2 to give 0.55 g (88% yield)1-[2-(trans-2-Butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzeneas an oil after purification by radial chromatography on a 4 mm silicaplate eluting with 100% hexane.

EXAMPLE 11 Tc-99m complex of1-[2-(trans-2-Butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene

1-(2-trans-2-Butenylthio)-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene was reacted with Tc-99m sodium pertechnetate by the procedure ofExample 7 to produce the Tc-99m complex of1-[2-(trans-2-butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene. HPLC (90% ethanol//H₂ O, 1.5 ml/min, Waters Radial-Pak C-18) Rt4.06 min, radiochemical purity 100%. TLC (70% hexane/diethyl ether) RF0.26, radiochemical purity 94%. Electrophoresis (0.05 M NaH₂ PO₄, pH4.5, 300 volts, 45 min) neutral.

EXAMPLE 12 2-Allylthio-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal (10 g, 6.7×10⁻² mol, 100M%) was dissolved in 150 ml tetrahydrofuran (distilled over sodium).Hexane-washed sodium hydride (3.86 g, 8×10⁻² mol, 120 M%) (50% in oil)was added to the solution. Allyl bromide (5.80 ml, 6.71×10⁻² mol, 100M%) was then added, and the mixture stirred at room temperature for 18hours. Methanol (50 ml) was added and the mixture was extracted with2×100 ml diethyl ether. The combined ether layers were then washed with100 ml saturated NaCl and dried over anhydrous Na₂ SO₄. The ether wasremoved on a rotary evaporator to yield 12.05 g (95% yield) of2-allylthio-2-methylpropanalethylenedioxy acetal as a yellow oil.

EXAMPLE 13 2-Allylthio-2-methylpropanal

2-allylthio-2-methylpropanalethylenedioxy acetal (12.50 g, 6.4×10⁻² mol)was heated at reflux for 5 hours in a mixture of 100 ml tetrahydrofuranand 50 ml 0.15 M HCl. Thereafter, the aqueous layer was extracted with2×100 ml diethyl ether. The combined organic extracts were then washedwith 100 ml saturated NaCl and dried over anhydrous Na₂ SO₄. The solventwas removed on a rotary evaporator to give 7.10 g (77% yield) of2-allylthio-2-methylpropanal as a yellow oil.

EXAMPLE 141-(2-Allylthio-2-methylpropylamino)-2-(2-Mercapto-2-methylpropylamino)-benzene

2-Amino-1-(2-mercapto-2-methylpropylamino)benzene (3.5 g, 1.78×10⁻² mol)and 2-(allylthio)-2-methylpropanal (3.85 g, 2.67×10⁻² mol, 150 M%) weredissolved in 200 ml methanol. Glacial acetic acid (2.05 ml, 3.56×10⁻²,200 M%) and sodium cyanoborohydride (3.36 g, 5.35×10⁻² mol, 300 M%) werethen added. The reaction was stirred at room temperature for 18 hr, then100 ml 0.5 M HCl was added and the mixture was extracted with 2×100 mldiethyl ether. The combined organic extracts were washed with 100 mlsaturated NaHCO₃, then with 100 ml saturated NaCl. The ether layer wasdried over anhydrous Na₂ SO₄, and the solvent was removed on the rotaryevaporator. The crude product (6.7 g) was purified by filtration througha 600 ml sintered glass funnel filled silica bed, using 95%hexane/diethyl ether as the eluting solvent to give 4 g (70% yield) of1-(2-allylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino]benzeneas a yellow oil.

EXAMPLE 15 Tc-99m complex of1-(2-Allylthio-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene

1-[2-Allythio-2-methylpropylamino]-2-mercapto-2-methylpropylamino)benzene was reacted with Tc-99m sodium pertechnetate by the method ofExample 7. HPLC (90% ethanol:H₂ O, 1.5 ml/min, C18 5 micron Nova Pak)3.58 min (97%). TLC (50% diethyl ether: chloroform) RF 0.73,radiochemical purity 96%. Electrophoresis (0.05 M NaH₂ PO₄, pH 4.5, 300volts, 30 min) neutral.

EXAMPLE 16 2-[3-Butenylthio]-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal (7 g, 4.69×10⁻² mol) wasdissolved in 100 ml tetrahydrofuran (distilled over sodium).Hexane-washed sodium hydride (2.70 g, 5.62×10⁻² mol, 120 M%) (50% inmineral oil) and 4-bromo-1-butene (4.80 ml, 4.60×10⁻² mol, 100 M%) werethen added, and the mixture was stirred at room temperature for 18hours. Methanol (50 ml) was then added, and the reaction mixture wasextracted with 2×100 ml diethyl ether. The combined organic extractswere washed with 100 ml saturated NaCl and dried over anhydrous Na₂ SO₄.The ether was removed on a rotary evaporator to yield 9.0 g (94% yield)of 2-[3-butenylthio]-2-methylpropanalethylene-dioxy acetal.

EXAMPLE 17 2-[3-Butenylthio]-2-methylpropanal

2-[3-Butenylthio]-2-methylpropanalethylenedioxy acetal (9.0 g, 4.43×10⁻²mol) was placed in a mixture of 100 ml tetrahydrofuran and 100 ml 0.5 MHCl. The solution was heated to reflux for 4 hours, then the aqueouslayer was extracted with 2×100 ml diethyl ether. The combined etherallayers were washed with 100 ml saturated NaCl and dried over anhydrousNa₂ SO₄. The solvent was removed on the rotary evaporator to give 6.3 g(90% yield) of 2-[3-butenylthio]-2-methylpropanal as a yellow oil.

EXAMPLE 181-[2-(3-Butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene

2-Amino-1-(2-mercapto-2-methylpropylamino)benzene (3.5 g, 1.78×10⁻² mol,100 M%) and 2-(3-butenylthio)-2-methylpropanal (4.23 g, 2.67×10⁻² mol,150 M%) were dissolved in 200 ml methanol. Glacial acetic acid (2.05 ml,3.56×10⁻² mol, 200 M%) and sodium cyanoborohydride (3.36 g, 5.35×10⁻²mol, 300 M%) were then added. After 17 hours, the reaction was quenchedby the addition of 100 ml 0.5 N HCl. The acidic solution was thenextracted with 2×100 ml diethyl ether. The combined organic extractswere washed with 100 ml saturated NaHCO₃, followed by 100 ml saturatedNaCl. The ether layer was then dried over anhydrous Na₂ SO₄. The solventwas removed on the rotary evaporator, and the residue was purified byfiltration through a 600 ml sintered-glass funnel silica bed, using 90%hexane/diethyl ether as the eluting solvent, to give 5 g (84% yield)1-[2-(3-butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)-benzeneas a yellow oil.

EXAMPLE 19 Tc-99m complex of1-[2-(3-Butenylthio)-2-methylpropylamino-2-(2-mercapto-2-methylpropylamino)benzene

1-[2-(3-Butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzenewas reacted with Tc-99m sodium pertechnetate by the method of Example 7to produce the Tc-99m complex of1-[2-(3-butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene.HPLC (90% ethanol:H₂ O, 1.5 ml/min, C18 5 micron Nova Pak) 3.86 min(96%). TLC (80% ethyl acetate:petroleum ether) Rf 0.45, radiochemicalpurity 95%.

EXAMPLE 20 2-(Propylthio)-2-methylpropanalethylenedioxy acetal

In a 100 ml round-bottom flask equipped with a nitrogen inlet andmagnetic stir bar, 2-mercapto-2-methylpropanalethylenedioxy acetal,(1.53 g, 1.03×10⁻² mol, 100 M%) and iodopropane (1.93 g, 1.14×10⁻² mol,110 M%) were combined in 50 ml of freshly distilled tetrahydrofuranunder nitrogen. Sodium hydride (0.27 g, 1.14×10⁻² mol, 110 M%) (50%mineral oil dispersion washed 3×with 20 ml petroleum ether) was added tothe reaction flask, causing gas evolution. The mixture was stirred at25° C. for 2 hr and was then quenched with 50 ml 0.5 M NaOH. The mixturewas extracted with 3×50 ml diethyl ether. The combined ether layers werewashed with 2×40 ml NaCl and were dried over anhydrous Na₂ SO₄. Removalof the solvent by rotary evaporation gave 2.10 g (100% yield) of2-(propylthio)-2-methylpropanalethylenedioxy acetal as a colorlessliquid.

EXAMPLE 21 2-Propylthio-2-methylpropanal

In a 250 ml round-bottomed flask equipped with a reflux condenser andnitrogen inlet, 2-(propylthio)-2-methylpropanalethyleneddioxy acetal(2.00 g, 1.05×10⁻² mol, 100 M%) was dissolved in 25 ml tetrahydrofuranand 25 ml 0.5 M HCl. The mixture was heated to reflux for 2 hr. Aftercooling to room temperature, the solution was extracted with 3×50 mldiethyl ether. The combined ether layers were washed with 50 ml H₂ O, 50ml saturated NaCl, and were dried over anhydrous Na₂ SO₄. Filtration andremoval of the solvent by rotary evaporation provided 1.37 g (89% yield)of 2-propylthio-2-methylpropanal as a colorless liquid.

EXAMPLE 222-(2-Mercapto-2-methylpropylamino)-1-[2-propylthio-2-methylpropylamino]benzene

2-Amino-1-(2-mercapto-2-methylpropylamino)benzene (0.40 g, 2.06×10⁻³mol) and 0.452 g (3.09×10⁻³ mol, 150 M%) of2-propylthio-2-methylpropanal were reacted by the method of Example 2 togive 0.239 g (40% yield) of2-(2-mercapto-2-methylpropylamino)-1-[2-propylthio-2-methylpropylamino]-benzeneas a colorless oil after purification by radial chromatography on a 4 mmsilica gel plate eluting with 200 ml 5% diethyl ether/petroleum etherand 100 ml 7% diethy ether/petroleum ether.

EXAMPLE 23 Tc-99m Complex of2-(2-Mercapto-2-methylpropylamino)-1-[2-propylthio-2-methylpropylamino]-benzene

2-(2-Mercapto-2-methylpropylamino)-1-(2-propylthio-2-methylpropylamino)benzene wasreacted as in Example 7 to produce the Tc-99m complex of2-(2-mercapto-2-methylpropylamino)-1-[2-propylthio-2-methylpropylamino]-benzene.Two main components were present in the reaction solution. The mixturewas purified by injecting 200 l of the reaction mixture into the HPLCand collecting fractions. The third fraction contained the desiredTc-99m complex (1.0 mCi/ml). HPLC (90% ethanol/H₂ O, 1.5 ml/min, WatersRadial-Pak C18) Rt 3.66 min, radiochemical purity 100%. TLC (30% ethylacetate/hexane) Rf 0.63, radiochemical purity 94%. Partition coefficient(1-octanol/0.1 M phosphate buffer pH 7.4) 33.

EXAMPLE 24 2-(2-Propynylthio)-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal, (14.80 g, 1.00×10⁻¹mol, 100 M%) was dissolved in 100 ml tetrahydrofuran. Propargyl chloride(8.06 ml, 1.00×10⁻¹ mol, 100 M%) and 4.80 g (1.2×10⁻¹ mol, 120 M%)sodium hydroxide dissolved in 10 ml water were added to the reactionsolution. The solution was stirred at 21° C. for 24 hr. Water (60 ml)was added and the reaction solution was extracted with 2×70 ml ether.The ether layers were combined, washed with 60 ml saturated sodiumchloride, and dried over sodium sulfate. The solvent was removed on therotary evaporator to give a crude oily product which was then distilledunder vacuum (bp 80°-81° C., 0.09 mmHg) to afford 12.60 g (68% yield) of2-(2-propynylthio)-2-methylpropanalethylenedioxy acetal as a colorlessoil.

EXAMPLE 25 2-(2-Propynylthio)-2-methylpropanal

2-(2-Propynylthio)-2-methylpropanalethylenedioxy acetal, (4.59 g,2.47×10⁻² mol, 100 M%) was dissolved in a mixture of 30 mltetrahydrofuran and 30 mnl 0.5 M HCl. The solution was heated at refluxfor 4 hr, cooled, and then extracted with 2×75 ml diethyl ether. Theether layers were combined, washed with 40 ml of saturated sodiumchloride solution, and dried (Na₂ SO₄). The solvent was removed under onthe rotary evaporator to afford 2-(2-propynylthio)-2-methylpropanal 3.26g (93% yield) as an oily product.

EXAMPLE 262-(2-Mercapto-2-methylpropylamino)-1-[2-(2-propynylthio)-2-methylpropylamino]benzene

2-Amino-1-(2 -mercapto-2-methylpropylamino)benzene (5.59 g, 2.85×10⁻²mol) and 2-(2-propynylthio)-2-methylpropanal (6.07 g, 4.28×10⁻² mol, 150M%) were mixed, then 125 ml methanol and 5.27 ml (5.7×10⁻² mol, 200 M%)acetic acid were added and solids were allowed to dissolve. Sodiumcyanoborohydride (5.39 g, 8.56×10⁻² mol, 300 M%) was added to thereaction solution in three equal portions. The reaction was stirred at21° C. for 17 hr, then quenched with 100 ml 0.5 M HCl, stirred for 15min, and then extracted with 2×150 ml ether. The ether layers werecombined, washed with 60 ml saturated NaCl solution and dried over Na₂SO₄. The solvent was removed on the rotary evaporator and the residuewas purified by filtration through flash silica in a 600 ml sinteredglass funnel 3/4 full of silica, eluting with 500 ml portions of2×hexane and 2×90% hexane/ether to produce 6.88 g (75% yield)2-(2-mercapto-2-methyl-propylamino)-1-[2-(2-propynylthio)-2-methylpropylamino]-benzene.

EXAMPLE 27 Tc-99m Complex of2-(2-Mercapto-2-methylpropylamino)-1-[2-(2-propynylthio)-2-methylpropylamino]benzene

2-(2-Mercapto-2-methylpropylamino)-1-(2-propynylthio)-2-methylpropylamino)-benzenewas reacted with Tc-99m sodium pertechnetate by the method of Example 7to produce the Tc-99m complex of2-(2-mercapto-2-methylpropylamino)-1-[2-(2-propynylthio)-2-methylpropylamino]benzene.The complex was purified by filtration through a 0.22 micron Millex GSfilter. HPLC (90% ethanol/H₂ O, 1.5 ml/min, Waters Radial-Pak C18) Et3.33 min, radiochemical purity 100%. TLC (70% hexane/ethyl acetate, Rf0.43, radiochemical purity 93%. Electrophoresis (0.05 M NaH₂ PO₄, pH4.5, 300 volts, 30 min) neutral.

EXAMPLE 28 2-Ethylthio-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal (1.99 g, 1.34×10⁻² mol,100 M%) and iodoethane (2.31 g, 1.48×10⁻² mol, 110 M%) were treated withsodium hydride (0.35 g, 1.48×10⁻² mol, 110 M%) in tetrahydrofuran (40ml) for 4 hr as described for Example 20. Extraction and solvent removalprovided 2.88 g (100% yield) of2-ethylthio-2-methylpropanalethylenedioxy acetal as a colorless liquid.

EXAMPLE 29 2-Ethylthio-2-methylpropanal

2-(Ethylthio)-2-methylpropanalethylenedioxy acetal, (2.88 g, 1.6×10⁻²mol) was heated for 2.5 hr in 0.5 M HCl (25 ml) and tetrahydrofuran (25ml) and isolated as described in Example 21 to give2-ethylthio-2-methylpropanal, 2.31 g (100% yield) as a yellow liquidcontaining traces of tetrahydrofuran.

EXAMPLE 301,2,3,6,7,8-Hexahydro-3,3,6,6,-tetramethyl-4,5,1,8-benzodithiadiazacyclodecine

o-Phenylenediamine (1.0 g, 1.00×10⁻² mol, 100 M%) was dissolved in asolution containing (2.06 g, 1.00×10⁻² mol, 100% M%) 2,2'-dithio-bis(2-methylpropanal) in 30 ml methanol. Sodium cyanoborohydride (1.89 g,3.00×10⁻² mol, 300 M%) was added to the 21° C. reaction solution. Aceticacid was added dropwise until the pH of the reaction solution was pH 5.5(pH paper), then the reaction was stirred under argon for 15 hr at 21°C. The reaction solution was poured into 200 ml 0.5 M HCl. The solutiongot cloudy and a soft brown lump formed. The lump was removed with aglass stirring rod and the acid solution was basified (with cooling)with sodium hydroxide pellets to pH 13. The basified solution wasextracted with 2×100 ml portions of ether. The ether layers werecombined and washed with 50 ml saturated sodium chloride solution. Thelayer was dried (Na₂ SO₄), filtered, and the solvent was evaporated toafford 1.4 g of crude product oil. The crude product was dissolved inchloroform and absorbed onto 5 g silica gel. The chloroform was removedon the rotary evaporator, leaving free flowing silica, which was pouredinto a 60 ml sintered glass 3/4 full of flash silica (Merck silica gel60, 230-400 mesh, 0.040-0.063 mm). The silica was washed with 200 ml5:25 hexanes/ether and upon rotary evaportion yielded 0.69 g (24.5%yield) of1,2,3,6,7,8-Hexahydro-3,3,6,6-tetramethyl-4,5,1,8-benzodithiadiazacyclodecineas a solid.

EXAMPLE 31 1,2-Bis(2-mercapto-2-methylpropylamino)benzene

1,2,3,6,7,8-Hexahydro-3,3,6,6-tetramethyl-4,5,1,8-benzodithiadiazacyclodecine(51.0 mg, 1.81 mmol) was placed in a 100 ml round-bottom flask. LiquidNH₃ (30 ml), condensed in a dry ice-acetone bath, was added to themixture. The suspension was stirred and 4-5 pieces of sodium metal wasadded which caused the reaction to become a deep blue color. After 2hours, stirring, 0.5 g ammonium chloride was added. The resultingcolorless solution was boiled to dryness at room temperature. Water (30ml) was added dissolving the white precipitate and the mixture wasextracted 2×100 ml with diethyl ether. The ether layers were combined,washed with saturated NaCl, dried with anhydrous Na₂ SO₄, filtered, andremoved on the rotary evaporator. The crude product was purified in aflash column (14×7 cm silica gel 60) using 1:1 chloroform/diethyl etheras the eluting solvent. The solvent of the desired fraction was removedon the rotary evaporator and the residue was dried in a vacuumdessicator to afford 0.28 g (37 % yield)1,2-bis(2-mercapto-2-methylpropylamino)benzene as an oil.

EXAMPLE 322-(2-Mercapto-2-methylpropylamino)-1-[2-ethylthio-2-methylpropylamino]benzene

In a 50 ml round-bottom flask,1,2-bis(2-mercapto-2-methylpropylamino)benzene (397 mg, 1.40 mmol) wasdissolved in 25 ml of tetrahydrofuran (freshly distilled from Na withbenzophenone). The solution was flushed with nitrogen for 5-10 min, andsodium hydride (40 mg, 1.55 mmol, 120 M%) [50% mineral oil dispersionwashed 3×10 ml petroleum ether] was added to the reaction flask causinggas evolution. After 10-15 min, ethyl iodide (196 mg, 1.26 mmol, 90 M%)was added dropwise by syringe. The mixture was allowed to stir for 40min, during which time a fine white precipitate formed. TLC indicated anew product with higher Rf. Five ml 0.5 M HCl was added, the solutionwas transferred to a separatory containing 50 ml 0.5 M HCl and themixture was extracted with 3×50 ml ether. The combined ether layers werewashed with 50 ml 0.5 M NaOH, 50 ml saturated NaCl and were dried overanhydrous Na₂ SO₄. Removal of the solvent by rotary evaporation provided315 mg (72%) of an oil. The crude product was purified by radialchromatography using a 2 mm silica gel plate and 100 ml petroleum ether,100 ml 2% diethyl ether/petroleum ether, 2×100 ml 5% diethylether/petroleum ether to elute the product. The fractions containing themono-alkylated product were combined and concentrated to give 246 mg(56% of2-(2-mercapto-2-methylpropylamino)-1-[2-ethylthio-2-methylpropylamino]benzene as a white solid.

EXAMPLE 332-(2-Mercapto-2-methylpropylamino)-1-[2-ethylthio-2-methylpropylamino]-benzene

2-Amino-1-(2-mercapto-2-methylpropylamino)benzene (0.433 g, 2.23×10⁻³mol) and 0.599 g (4.46×10⁻³ mol, 200 M%) 2-ethylthio-2-methylpropanalwere reacted by the method of Example 2 to give 0.307 (28% yield) of2-(2-mercapto-2-methylpropylamino)-1-[2-ethylthio-2-methylpropylamino]benzene as a colorless oil after purification by radial chromatographyon a 4 mm silica gel plate eluting with 300 ml 5% diethylether/petroleum ether.

EXAMPLE 34 Tc-99m complex of2-(2-Mercapto-2-methylpropylamino)-1-[2-ethylthio-2-methylpropylamino]-benzene

2-(2-mercapto-2-methylpropylamino)-1-[2-ethylthio-2-methylpropylamino]benzenewas reacted with Tc-99m sodium pertechnetate by the method of Example 7.The product was purified by filtration through a 0.22 micron Millex GSfilter to produce a 1.09 mCi/ml solution of the Tc-99m complex of2-(2-mercapto-2-methylpropylamino)-1-[2-ethylthio-2-methylpropylamino]benzene.

HPLC (90% ethanol/H₂ O, 1.5 ml/min, C18 Radial Pak) Rt 3.76 min,radiochemical purity 100%. TLC (50% diethyl ether/chloroform) Rf 0.71,radiochemical purity 98%. Electrophoresis (0.05 M NaH₂ PO₄, pH 4.5, 300volts, 45 min Whatman 3MM paper) neutral. Partition coefficient(octanol/H₂ O NaH₂ PO₄ pH 7.4) 81.

EXAMPLE 35 2-(1-Methylethylthio)-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal (1.62 g, 1.09×10⁻² mol,100 M%) and 2-iodopropane (2.05 g, 1.20×10⁻² mol, 110 M%) were treatedwith sodium hydride (0.29, 1.20×10⁻² mol, 110 M%) in tetrahydrofuran (50ml) for 24 hr as described in Example 20. Extraction and solvent removalas described in Example 20 provided 1.46 g (70% yield) of2-(1-methylethylthio)-2-methylpropanalethylenedioxy acetal as a lightyellow liquid.

EXAMPLE 36 2-(1-Methylethylthio)-2-methylpropanal

2-(1-Methylethylthio)-2-methylpropanalethylenedioxy acetal (1.46 g,7.68×10⁻³ mol) was heated for 2 hr in 0.5 M HCl (25 ml) andtetrahydrofuran (25 ml) and isolated as described in Example 21 to give2-(1-methylethylthio)-2-methylpropanal 1.35 g (100%) of a light yellowliquid containing traces of tetrahydrofuran.

EXAMPLE 372-(2-Mercapto-2-methylpropylamino)-1-[2-(1-methylethylthio)-2-methylpropylamino]benzene

2-Amino-1-(2-mercapto-2-methylpropylamino)benzene (0.515 g, 2.65×10⁻³mol) and 0.786 g (5.31×10⁻³ mol, 200 M%)2-(1-methylethylthio)-2-methylethylthio)-2-methypropanal were reacted bythe method of Example 2 to give2-(2-mercapto-2-methylpropylamino)-1-[2-(1-methylethylthio)-2-methylpropylamino]benzene0.244 g (28% yield) as a colorless oil after purification by radialchromatography on a 2 mm silica gel plate eluting with 100 ml 100%petroleum ether and 200 ml 5% diethyl ether/petroleum ether.

EXAMPLE 38 Tc-99m complex of2-(2-Mercapto-2-methylpropylamino)-1-[2-(1-methylethylthio)-2-methylpropylamino]benzene

2-(2-Mercapto-2-methylpropylamino)-1-[2-(1-methylethylthio)-2-methylpropylamino]benzene was reacted with sodium pertechnetate Tc-99m according to themethod of Example 7 to produce the Tc-99m complex of2-(2-mercapto-2-methylpropylamino)-1-[2-(1-methylethylthio)-2-methylpropylamino] benzene. The product was purified by injecting thecrude mixture into the HPLC and collecting fractions.

EXAMPLE 391-[2-Methylthio-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene

1,2-Bis (2-Mercapto-2-methylpropylamino)benzene (0.47 g, 1.69×10⁻³ mol),and 0.09 g (1.85×10⁻³ mol, 110 M%) sodium hydride were dissolved in 25ml tetrahydrofuran. Methyl iodide (0.080 ml, 1.27×10⁻³ mol, 75 M%) wasadded, and the mixture was stirred under nitrogen for 1 hour. The excesshydride was destroyed by the slow addition of 10 ml 0.5 M HCl. Themixture was shaken with a mixture of 100 ml ether and 100 ml 0.5 N HCl.The aqueous layer was extracted with an additional 50 ml portion ofether, and the combined ether layers were washed with 100 ml saturatedNaCl. The ether layer was then dried over anhydrous Na₂ SO₄. Rotaryevaporation yielded 0.30 g (94% yield) of 1-[2-methylthio-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene as ayellow oil. Isolation was performed by radial chromatograph on a 1 mmsilica plate, using petroleum ether: ethyl acetate-80:20 as the elutingsolvent to give yielding a mixture of the1-[2-methylthio-2-methylpropyl-amino]-2-(2-mercapto-2-methylpropylamino)benzene, S,S'-dimethyl, and thedithiol starting material.

EXAMPLE 401-[2-(2-Methyl-2-propenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene

1,2-Bis (2-mercapto-2-methylpropylamino)benzene (0.304 g, 1.07×10⁻³ mol)was dissolved in 15 ml tetrahydrofuran. Sodium hydride (0.06 g,1.25×10⁻³ ml, 116 M%) and 0.095 ml (9.63×10⁻⁴ mol, 90 M%)3-chloro-2-methylpropene were added. The mixture was stirred at roomtemperature, under nitrogen, for 1.5 hours. The reaction mixture wasworked up as stated in Example 39. Product was isolated by radialchromatography on a 1 mm silica plate using hexane:ethyl acetate-90:10as the eluting solvent to give 100 mg (27% yield) as a mixturecontaining 50% of1-[2-(2-methyl-2-propenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene11% of the dithiol and 35% of the disubstituted compound.

EXAMPLE 412-(2-Butylthio-2-methylpropylamino]-1-(2-mercapto-2-methylpropylamino)benzene

1,2-Bis (2-mercapto-2-methylpropylamino)benzene (0.17 g, 6.1×10⁻⁴ mol,120 M%) and 0.07 g (5.1×10⁻⁴ mol, 100 M%) 1- bromobutane were dissolvedin 25 ml tetrahydrofuran (freshly distilled over Na). Sodium hydride(0.03 g, 6.25×10⁻⁴ mol, 102 M%) was then added. The mixture was stirredat room temperature under nitrogen for 3 hours. The reaction mixture wasworked up as in Example 40. The product was isolated by radialchromatography on 1 mm silica plate, using hexane: ethyl acetate as theeluting solvent, giving 40 mg (23% yield)2-(2-butylthio-2-methylpropylamino]-1-(2-mercapto-2-methylpropylamino)benzeneas a yellow oil.

EXAMPLE 422-(2-Mercapto-2-methylpropylamino)1-[2-(1-methylpropylthio)-2-methylpropylamino)benzene

1,2-Bis (2-mercapto-2-methylpropylamino)benzene (287 mg, 1.01 mmol, 100M%) was treated with sodium hydride (24 mg, 1.01 mmol, 100 M%) and2-iodobutane (162 mg, 0.90 mmol, 90 M%) as described in Example 32. Theproduct was purified twice by successive radial chromatography using 3%ether/petroleum ether to elute the product. Concentration of the desiredfractions gave 71 mg (21%) of2-(2-mercapto-2-methylpropylamino)-1-[2-(1-methylpropylthio-2-methylpropylamino)benzenea colorless oil.

EXAMPLE 43 Tc-99m complex of2-(2-Butylthio)2-methylpropylamino]-1-(2-mercapto-2-methylpropylamino)-benzene

2-(2-(Butylthio)2-methylpropylamino]-1-(2-mercapto-2-methylpropylamino)benzenewas reacted with Tc-99m sodium pertechnetate by the method of Example 7to produce Tc-99m complex of2-(2-butylthio)2-methylpropylamino)-1-(2-mercapto-2-methylpropylamino)benzene.The complex was purified by filtration through Millex GS and Jelco 5micron fitlers. HPLC (90% ethanol/H 2 O, 1.5 ml/min, C18 5 micron RadialPak) Rt 4.4 min (99%). TLC (50% diethyl ether/chloroform) Rf 0.89,radiochemical purity 92%. Electrophoresis (0.05 M NaH₂ PO₄, buffer pH4.5 constant 300 volts, 30 min) neutral.

EXAMPLE 44 Tc-99m complex of1-[2-Methylthio-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)-benzene

1-[2-Methylthio-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzenewas reacted with Tc-99m sodium pertechnetate by the method of Example 7to produce the Tc-99m complex of1-[2-methylthio-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene.HPLC (80% ethanol/H₂ O, 1.5 ml/min, C18 5 micron Nova Pak) Rt 4.34 min(92%). TLC (50% chloroform/diethyl ether) Rf 0.75, radiochemical purity95%. Electrophoresis (0.05 M NaH₂ PO₄, pH 4.5, 300 volts, 30 min)neutral.

EXAMPLE 45 Tc-99m complex of1-[2-(2-Methyl-2-propenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene

1-[2-(2-Methyl-2-propenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)-benzenewas reacted with Tc-99m sodium pertechnetate by the method of Example 7to produce Tc-99m complex of1-[2-(2-methyl-2-propenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene.HPLC (90% ethanol:H₂ O, 1.5 ml/min, C18 5 micron Nova Pak) Rt 3.65 min(100%). TLC (50% diethyl ether: chloroform (Rf 0.58, radiochemicalpurity 96%. Electrophoresis (0.05 M NaH₂ PO₄, pH 4.5, 300 volts, 30 min)neutral.

EXAMPLE 46 Tc-99m complex of2-(2-Mercapto-2-methylpropylamino)-1-[2-(1-methylpropylthio)-2-methylpropylamino)benzene

2-(2-Mercapto-2-methylpropylamino)-1-(2-(1-methylpropylthio)-2-methyl-propylamino)benzenewas reacted with sodium pertechnetate Tc-99m according to the method ofExample 7 to produce the Tc-99m complex of2-(2-mercapto-2-methylpropylamino)-1-[2-(1-methylpropylthio)-2-methylpropylamino)benzene.The produce was purified by filtration through a 0.22 micron Millex GSfilter. HPLC (90% ethanol/H₂ O, 1.5 ml/min, Waters Radial-Pak C18) Rt4.01 min, radiochemical purity 95.5%. TLC (30% ethyl acetate/hexane) Rf0.33, radiochemical purity 93.2%; (ethyl acetate/methanol/water/15 M NH₄OH-- 86:10:3:1) Rf 0.83, radiochemical purity 97.5%. Electrophoresis(0.05 M NaH₂ PO₄, pH 4.5, 300 volts, 45 min, Whatman 3MM paper) neutral.

EXAMPLE 471-(2-Vinylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene

1,2,3,6,7,8-Hexahydro-3,3,6,6-tetramethyl-4,5,1,8-benzodithiadiazacyclodecine(0.34 g, 1.21×10⁻³ mol, 100 M%) was placed in a flame dried round bottomunder nitrogen. Vinylmagnesium bromide (1.0 M in tetrahydrofuran (13.6ml, 1.36×10⁻² mol, 1124 M%) was added to the solid and the solution washeated at reflux for 1.5 hr. The reaction was quenched with 2×75 mlether. The ether layers were combined, washed with 40 ml saturatedsodium chloride solution and dried over Na₂ SO₄. The ether was removedon the rotary evaporator to obtain the crude oily product. The productwas purified by radial chromatography on a 2 mm silica plate and elutingwith 90% petroleum ether/ethyl acetate to obtain 0.15 g (40%)1-(2-vinylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzeneas an oil.

EXAMPLE 48 Tc-99m complex of1-(2-Vinylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene

1-(2-Vinylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzenewas reacted with Tc-99m sodium pertechnetate by the method of Example 7to produce the Tc-99m complex of1-(2-vinylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzenein 68% yield. HPLC (90% ethanol:H₂ O, 1.5 ml/min, C18 5 micron Nova Pak)3.46 min (93%). TLC (10% ethyl acetate:petroleum ether) Rf 0.40,radiochemical purity 94%. Electrophoresis (0.05 M NaH₂ PO₄ buffer, pH4.5, 300 volts, 30 min) neutral.

EXAMPLE 49 2-Amino-3-(2-mercapto-2-methylpropylamino)toluene

2,3-Diaminotoluene (1.50 g, 1.22×10⁻² mol) and 1.08 g (1.23×10⁻² mol)isobutylene sulfide were placed in a Teflon-lined bomb and heated to110° C. for 8 hours. After cooling to room temperature, the oily residuewas dissolved in 100 ml ethyl acetate and washed with 100 ml water,followed by 100 ml saturated NaCl. The ethyl acetate was then dried overanhydrous Na₂ SO₄ and removed on the rotary evaporator. The residue (2.0g, 80% yield) was purified on a 500 ml sintered glass funnel silica bed,using 90% hexane:ethyl acetate as the eluting solvent, to give 0.40 g(16% yield) of 2-amino-3-(2-mercapto-2-methylpropylamino)toluene as anoil.

EXAMPLE 50 2-Butylthio-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal (3 g, 2.0×10⁻² mol) and3.03 g (2.2×10⁻² mol, 110 M%) 1-bromobutane were dissolved in 25 mltetrahydrofuran (freshly distilled over sodium). The system was purgedwith nitrogen and 1.16 g (2.4×10⁻² mol, 120 M%) sodium hydride (washedwith 2×10 ml portions of hexane) was added. The solution was stirred atroom temperature under nitrogen for 24 hours. Thereafter, the excesshydride was destroyed by the addition of 10 ml methanol. The solutionwas shaken with a mixture of 100 ml diethyl ether and 100 ml 0.5 M NaOH.The ether layer was washed with 100 ml saturated NaCl, then dried overanhydrous Na₂ SO₄. Rotary evaporation yielded 3.73 g (90% yield) of2-butylthio-2-methylpropanalethylenedioxy acetal as an oil.

EXAMPLE 51 2-Butylthio-2-methylpropanal

2-Butylthio-2-methylpropanalethylenedioxy acetal, (3.73 g, 1.82×10⁻²mol) was placed in a 100 ml round-bottom flask, then a mixture of 20 mlmethanol, 20 ml H₂ O, and 5 ml 12 M HCl was added, and the solution wasrefluxed for 2 hours. The mixture was extracted with 100 ml diethylether and 100 ml water. The ether layer was then dried over Na₂ SO₄.Rotary evaporation yielded 2.4 g (80% yield) of2-butylthio-2-methylpropanal as a yellow oil.

EXAMPLE 522-(2-Butylthio)-2-methylpropylamino)-1-(2-mercapto-2-methylpropylamino)-3-methylbenzene

2-Amino-3-(2-mercapto-2-methylpropylamino)toluene (0.69 g, 3.3×10⁻³ mol)and 0.91 g (5.25×10⁻³ mol, 160 M%) 2-butylthio-2-methylpropanal weredissolved in 50 ml methanol and 0.37 ml (6.6×10⁻³ mol, 200 M%) glacialacetic acid was added, followed by 0.62 g (9.9×10⁻³ mol, 300 M%) sodiumcyanoborohydride. The mixture was stirred at room temperature undernitrogen for 20 hr, then 100 ml 0.5 M HCl was added and the mixture wasextracted with diethyl ether then dried over anhydrous Na₂ SO₄, andremoved on the rotary evaporator. The residue (0.80 g, 69% yield) waspurified by radial chromatography on a 4 mm silica gel plate, usingpetroleum ether: ethyl acetate-95% as the eluting solvent, to give2-(2-butylthio)-2-methylpropylamino)-1-(2-mercapto-2-methylpropylamino-3-methylbenzene,0.40 g (34% yield) as a yellow oil.

EXAMPLE 53 Tc-99m complex of2-(2-Butylthio-2-methylpropylamino)-1-(2-mercapto-2-methylpropylamino)-3-methylbenzene

2-[2-(Butylthio)-2-methylpropylamino]-1-(2-mercapto-2-methylpropylamino-3-methylbenzenewas reacted with Tc-99m sodium pertechnetate by the method of Example 7to produce Tc-99m complex of2-(2-butylthio)-2-methylpropylamino)-1-(2-mercapto-2-methylpropylamino)-3-methylbenzene.The complex was purified by filtration through Millex GS and Jelco 5micron filters. HPLC (90% ethanol/H₂ O) 1.5 ml/min, C18 5 micron RadialPak) Rt 4.74 min (99%). TLC (50% diethyl ether/chloroform) Rf 0.95,radiochemical purity 86%. Electrophoresis (0.05 M NaH₂ PO₄, buffer pH4.5, 300 volts, 30 min) neutral.

EXAMPLE 54 2-Cyclopropylmethylthio-2-methylpropanalethylenedioxy acetal

2-Mercapto-2-methylpropanalethylenedioxy acetal (3.36 g, 2.27×10⁻² mol,100 M%) was dissolved in 100 ml anhydrous tetrahydrofuran. Hexane-washedsodium hydride (1.20 g, 2.50×10⁻² mol, 110 M%) (50% in oil) was added tothe reaction mixture which was stirred at 21° C. for 1.5 hr and thenquenched with 100 ml H₂ O. The reaction solution was extracted with 2×60ml diethyl ether. The ether layers were combined, washed with 40 mlsaturated NaCl solution and then dried (Na₂ SO₄). The solvent wasremoved on the rotary evaporator to afford 4.03 g (88% yield) of2-cyclopropylmethylthio-2-methylpropanal-ethylenedioxy acetal as an oil.

EXAMPLE 55 2-Cyclopropylmethylthio-2-methylpropanal

2-Cyclopropylmethylthio-2-methylpropanalethylenedioxy acetal, (3.77 g,1.87×10⁻² mol, 100 M%) was placed in a mixture of 15 ml tetrahydrofuranand 40 ml 0.5 M HCl and heated at reflux for 2 hr, then quenched with 40ml H₂ O. The reaction was extracted with 2×60 ml diethyl ether, washedwith 40 ml saturated NaCl solution, and dried over Na₂ SO₄. The solventwas removed on the rotary evaporator to afford 2.88 g (98% yield) of2-cyclopropylmethylthio-2-methylpropanal as an oil.

EXAMPLE 561-(2-Cyclopropylmethylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene.

2-Amino-1-(2-mercapto-2-methylpropylamino)benzene (0.43 g, 2.19×10⁻³mol) and 0.82 g (5.19×10⁻³ mol, 237 M%)2-cyclopropylmethylthio-2-methylpropanal were reacted by the method ofExample 2 to yield 0.63 g (85%) of1-(2-cyclopropylmethylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzeneas an oil product after purification by filtration through flash silicain a 350 ml sintered glass funnel, eluting with 200 ml portions of2×100% hexane, 3×90% hexane/ether, 2×80% hexane/ether.

EXAMPLE 57 Tc-99m complex of1(2-Cyclopropylmethylthio-2-methylpropylamino)-2-(2-mercapto-2-methyl-propylamino)benzene.

1-[2-Cyclopropylmethylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene was reacted with Tc-99m sodium pertechnetate by the method ofExample 7 to produce Tc-99m complex of1-[2-cyclopropylmethylthio-2-methylpropylamino)-2-(2-mercapto-2-methyl-propylamino)benzene. The complex was purified by filtration through a 0.22 micronMillex GS filter. HPLC (80% ethanol/H₂ O, 1.5 ml/min, Waters Radial-PakC18) Rt 4.99 min, radiochemical purity 100%. TLC (70% hexane/ethylacetate) Rf 0.42, radiochemical purity 98%. Electrophoresis (0.05 M NaH₂PO₄, pH 4.5, 300 volts, 45 min) neutral.

EXAMPLE 58 Preparation of a Technetium Kit

In a 10 ml crimp vial, 3.6 mg (1×10⁻⁵ moles) of the ligand of formula Ieach as the compound as prepared in Example 26 was dissolved in 5 dropsethanol. The ethanol was then removed with a nitrogen stream, to leave athin film of solid. Argon purged sterile H₂ O (9.5 ml) and 0.40 g2-hydroxypropyl-beta-cyclodextrin (HPCD) were then added. The mixturewas sonicated for 10 minutes, and stirred on the vortex mixer for anadditional 10 minutes. The mixture was repurged with argon, sealed andcrimpled. Stannous chloride (0.60 ml 1 mM) as then added. The 1 MMstannous chloride solution was prepared by the addition of 9.5 mganhydrous SnCl₂ in 50 ml argon-purged water. The mixture was thenfiltered under argon through a Millex GS filter into six vented 10 mlvials. Approximately 1 ml was dispensed into each vial. The vials werethen placed in a vacuum dessicator overnight at 0.5 Torr to give a whitesolid. Thereafter, the vials were flushed with argon, sealed andcrimped. The vials were stored at room temperature protected from light.

EXAMPLE 59 Tc-99m Labeling of the Kit

A kit vial prepared in Example 58 was reconstituted in 1 ml sterile,purged H₂ O. The mixture was sonicated for 5 minutes, to give a clearsolution. Tc-99m NaTcO₄ (1 ml 10 mCi/ml) was then added to each vial.Radiolabeling yields were determined by TLC using ethylacetate/petroleum ether (20:80) as the eluting solvent.

EXAMPLE 60 Biological Evaluation of Tc-99m Complexes

Distribution of the Tc-99m labeled compounds was evaluated in rats.Female Sprague-Dawley rats weighing 140 to 220 g (average 170 g) wereanesthetized with sodium pentobarbital and were injected in a tail veinwith from 0.05 to 10 mCi of the Tc-99m labeled complex in a volume of0.2 to 0.5 ml. At least two rats were injected for each time point.

The animals were sacrificed at 5 and 30 minutes after injection andselected organs were removed; the tails were discharged to avoidinterference from the injection site. The radioactivity in each organwas measured at a standard geometry with a thallium iodide-activatedsodium iodide scintillation detector adjusted for the 140 KeV emissionof Tc-99m. The organs were also weighed to one hundredth of a gram andthe activity was calculated as a percent of administered dose per gram.The results are reported in the following table.

                                      TABLE 1                                     __________________________________________________________________________    Biological Distribution of Tc-99m Complexes in Rats (Pentobarbital            Anesthesia)                                                                   % Injected Dose/Gram Tissue (average of 2 rats)                               Patent                                                                        5 min                    30 min                                               Example          Brain:                                                                            Heart:          Brain:                                                                            Heart:                               #    Blood                                                                             Brain                                                                             Heart                                                                             Blood                                                                             Blood                                                                             Blood                                                                             Brain                                                                             Heart                                                                             Blood                                                                             Blood                                __________________________________________________________________________    11   0.26                                                                              0.50                                                                              2.40                                                                              1.94                                                                               9.29                                                                             0.19                                                                              0.49                                                                              1.13                                                                              2.58                                                                              6.01                                 57   0.20                                                                              0.54                                                                              2.12                                                                              2.63                                                                              10.34                                                                             0.11                                                                              0.47                                                                              0.86                                                                              4.18                                                                              7.68                                 27   0.47                                                                              0.82                                                                              5.26                                                                              1.75                                                                              11.28                                                                             0.19                                                                              0.67                                                                              3.28                                                                              3.54                                                                              17.34                                 7   0.20                                                                              0.44                                                                              2.64                                                                              2.17                                                                              13.00                                                                             0.12                                                                              0.48                                                                              1.33                                                                              4.11                                                                              11.36                                23   0.35                                                                              0.75                                                                              2.43                                                                              2.11                                                                               6.86                                                                             0.23                                                                              0.69                                                                              1.01                                                                              3.06                                                                              4.44                                 38   0.34                                                                              0.73                                                                              2.48                                                                              2.13                                                                               7.22                                                                             0.27                                                                              0.67                                                                              1.04                                                                              2.44                                                                              3.78                                 46   0.23                                                                              0.64                                                                              2.96                                                                              2.81                                                                              12.94                                                                             0.15                                                                              0.57                                                                              1.28                                                                              3.71                                                                              8.35                                 34   0.14                                                                              0.88                                                                              2.47                                                                              6.26                                                                              17.48                                                                             0.11                                                                              0.71                                                                              1.02                                                                              6.21                                                                              8.94                                 53   0.76                                                                              0.29                                                                              1.58                                                                              0.38                                                                               2.06                                                                             0.41                                                                              0.29                                                                              0.85                                                                              0.71                                                                              2.09                                 43   0.81                                                                              0.41                                                                              2.02                                                                              0.51                                                                               2.50                                                                             0.35                                                                              0.43                                                                              0.96                                                                              1.24                                                                              2.77                                 44   0.12                                                                              0.78                                                                              1.48                                                                              6.46                                                                              12.16                                                                             0.07                                                                              0.44                                                                              0.50                                                                              6.19                                                                              7.12                                 45   0.30                                                                              0.60                                                                              3.40                                                                              2.01                                                                              11.40                                                                             0.19                                                                              0.55                                                                              2.24                                                                              2.90                                                                              11.81                                48   0.61                                                                              0.56                                                                              3.51                                                                              0.92                                                                               5.75                                                                             0.30                                                                              0.57                                                                              3.05                                                                              1.92                                                                              10.32                                19   0.36                                                                              0.80                                                                              3.40                                                                              2.20                                                                               0.32                                                                             0.18                                                                              0.69                                                                              1.52                                                                              3.76                                                                              8.30                                 15   0.27                                                                              0.99                                                                              4.37                                                                              3.61                                                                              15.97                                                                             0.13                                                                              0.75                                                                              2.25                                                                              5.63                                                                              16.77                                __________________________________________________________________________

EXAMPLE 61 2-Acetylthio-2-methylpropanoic acid

Three 100 g bottles of 2-bromo-2-methylpropanoic acid with the lidsloosened slightly were placed in a boiling water bath. The moltencontents of the bottles were poured into a tared 250 ml erlenmeyer toobtain 302.35 g (1.810 mol, 100 M%) of the acid.

Dimethylformamide (DMF), 100 ml was poured into a 4 l indented 3 neckround bottom flask equipped with a nitrogen bubbler and an overheadstirrer (glass shaft, teflon paddle). The hot 2-bromo-2-methylpropionicacid was then added to the flask through a powder funnel. The flask andthe funnel were rinsed with 4×100 ml portions of DMF and were added tothe reaction flask. A thermometer was placed in the third neck and thestirred solution was cooled under an atmosphere of nitrogen to -45° C.by placing it in a methanol/water 50:50 dry ice bath. The thermometerwas removed and potassium carbonate 250.21 g (1.810 mol, 100 M%) wasadded through a powder funnel over a 5 minute period. The reactionmixture warmed to -40° C. but there was no apparent reaction and thecarbonate did not dissolve. The soluton was diluted with 200 ml DMF andpotassium thioacetate 407.10 g (3.564 mol, 196.9 M%) was added through apowder funnel over a 5 minute period. The powder funnel was rinsed with300 ml DMF which was added to the reaction solution which had warmed to-30° C. The reaction was allowed to slowly warm up as the dry ice wasconsumed. When the reaction temperature reached -10° C. the reactionbegan to bubble. The reaction was allowed to warm slowly to roomtemperature and was stirred under nitrogen for 22 hours. Water, 2 1, and500 ml concentrated hydrochloric acid were mixed and cooled to 9° C. inan ice bath. The tan colored reaction mixture was slowly poured into thestirred acid solution over a 25 minute period. The reaction flask waswashed with 2×100 ml portions of deionized water which was added to theacid solution (10° C., pH 1.5). The acid solution was poured into a 4 lseparatory funnel and was extracted sequentially with 3×500 ml and 1×250ml ethyl acetate. Each organic extract was washed with a separate 100 mlportion of saturated sodium chloride solution. The organic extracts werecombined and dried over 400 g of anhydrous sodium sulfate. The solutionwas filtered through a fluted filter paper into a 2,000 ml round bottomflask and the solvent was removed in two portions under reduced pressureon the rotary evaporator. The sodium sulfate was washed with 3×100 mlportions of ethyl acetate which were filtered into the 2,000 ml roundbottom. After all the solvent was removed, the rotary evaporator wasconnected to the high-vacuum pump and the water bath was heated to 100°C. The product was removed after 1.5 hour to afford 241.07 g of thecrude brown oily product which crystallized on cooling. The crystallinemass was placed under high vacuum at 22° C. for 16 hours to afford240.51 g (82% yield) of the crude crystalline2-acetylthio-2-methylpropanoic acid.

EXAMPLE 62 2-Mercapto-2-methylpropanoic acid

2-Acetylthio-2-methylpropanoic acid 230.41 g (1.422 mol, 100 M%) wasplaced in a 2 l round bottom flask, equipped with a magnetic stir bar.The crude solid material was dissolved in 250 ml methanol whilestirring.

Methanol, 900 ml, was poured into a 3-l three-neck flask equipped with amagnetic stir bar and a reflux condenser with a nitrogen bubbler on top.The other two necks were stoppered until the flask was flushed withnitrogen. One of the stoppers was removed and, hexane washed sodiumspheres (73.16 g, 3.18 mol, 224 M%) were added through a powder funnelover a 20 minute period. The methanol solution bubbled vigorously andwas heated to reflux by the chemical reaction.

Both methanol solutions were chilled in an ice bath after all of thesodium had dissolved. The sodium methoxide solution was then poured, allat once, into the chilled solution of 2-acetlythio-2-methylpropanoicacid which warmed to 38° C. The reaction solution was cooled to 20° C.then the ice bath was removed and the solution was stirred at roomtemperature for 25 minutes. The reaction solution was then chilled in anice bath to 10° C. over 20 minutes and poured into a 6 l erlenmeyerflask containing a solution of 300 ml concentrated HCl and 700 mldeionized water at 10° C. This solution was extracted with 1×1 l and2×500 ml portions of ethyl acetate. The ethyl acetate extracted waswashed with the same two 300 and 200 ml portion of saturated sodiumchloride solution. The organic layers were combined and the solvent wasremoved on the rotary evaporator to afford an oil which was dissolved in250 ml ethyl acetate. The ethyl acetate solution was washed with 150 mlsaturated sodium chloride solution and then the organic layer was driedover 208 g anhydrous sodium sulfate. The ethyl acetate solution wasfiltered through a fluted filter paper into a 2 l round bottom flask.The solvent was removed under reduced pressure on the rotary evaporator.The rotary evaporator was connected to the vacuum pump for 15 minutes(0.10 mmHg 51° C. water bath) to afford 160.661 g of2-mercapto-2-methylpropanoic acid as a brown oil (94% yield) whichcrystallized when cooled in the refrigerator.

EXAMPLE 63 2-Methyl-2-(2-propynylthio)propanoic acid

Potassium carbonate, 346.26 g (2.505 mol, 220 M%) was dissolved in 1,750ml deionized water in a 4 l indented round bottom flask equipped with amagnetic stir bar. The carbonate solution was cooled in an ice bath to6° C.

The 2-mercapto-2-methylpropanoic acid was dissolved in a solutioncontaining 1 l methanol and 186.67 g (2.505 mol, 200 M%) propargylchloride. This solution was then added to the cold carbonate solution.The round bottom that had contained the acid was washed with 2×100 mlportions of methanol added to the reaction solution which was 15° C. Thereaction was removed from the ice bath 30 minutes after the initialmixing and stirred at room temperature (22° C.) for 3.5 hours. Thereaction was quenched by pouring it slowly into a chilled solutioncontaining 350 ml concentrated hydrochloric acid and 1500 ml deionizedwater. The acid solution was extracted with 3×400 ml portions of ethylacetate. The organic layers were combined and washed with 2×300 mlportions of saturated sodium chloride solution, then dried over 212 ganhydrous sodium sulfate. The dried organic solution was filteredthrough a sodium sulfate. The dried organic solution was filteredthrough a fluted filter paper. The solvent was removed under reducedpressure on the rotary evaporator. The crude oily product was thensubjected to high-vacuum (0.09 mmHg) for 30 minutes at 40° C. to obtain172.13 g of crude brown oil (86.97% yield) which crystallized whenchilled. Ethyl acetate, 210 ml, was added to the crude crystallineproduct which had been stored 2 days in the refrigerator. White solidremained after all of the crude product went into solution. The solutionwas then filtered under vacuum through a 60 ml sintered glass funnel 1/2full of Celite. The round bottom and the filter were washed with 3×50 mlportions of ethyl acetate. The filtrates were combined and the solventwas removed to afford 170.20 g of crude oily product in a 500 ml roundbottom flask. The round bottom was then equipped with 16.5 cm 14/20Vigreaux distillation column topped with a short path still head and a 3necked cow. The product was distilled at 0.2 mmHg, 104°-109° C. tocollect 118.69 g (fraction #2) of purified2-methyl-2-(2-propynylthio)-propanoic acid product (60% yield) whichcrystallized on standing.

EXAMPLE 64 2-Amino-2-(2-mercapto-2-methylpropylamino)benzene

In a 200 ml pressure bottle, 30 g (0.34 mol, 100 ml %) isobutylenesulfide and 51 g (0.47 mol, 140 mol %) o-phenylenediamine (Synder et al.J. Am. Chem. Soc. 69:2672-2674, 1947) were dissolved in 20 ml ethanol.The mixture was placed in a 100° C. oil bath, with stirring, for 5hours. The vessel was allowed to cool to room temperature, and the crudemixture was transferred to a 500 ml round bottom flask. The ethanol wasremoved on a rotary evaporator to give 77 g of a heterogeneous brownoil. The crude product was diluted with 200 ml diethyl ether and washedwith 3×200 ml 0.5 N NaOH. The combined base layers were then acidifiedto pH 1 by the slow addition of 40 ml concentrated HCl. The acid layerwas extracted with 3×200 ml diethyl ether. The pH of the aqueous layerwas then adjusted to pH 4 by the addition of 9 g sodium hydroxidepellets, and extracted with 3×200 ml diethyl ether. The combined etherlayers from the pH 4 extract were washed with 100 ml saturated NaCl anddried over 18 g anhydrous sodium sulfate. The solvent was then removedon a rotary evaporator to give 2.6 g (40% yield) of2-amino-1-(2-mercapto-2-methylpropylamino)benzene as a gold oil whichsolidified.

EXAMPLE 652-(2-Mercapto-2-methylpropylamino)-1-(2-methylpropylamido)benzene

In a 500 ml round bottom flask equipped with a N₂ inlet and a refluxcondensor, 22 g (0.14 mol, 100 ml %)2-methyl-2-(2-propynylthio)propanoic acid was dissolved in 100 mltoluene. Thionyl chloride (15.3 ml, 0.21 mol, 150 mol %) was added inone portion. The mixture was heated at reflux for 1 hour. Gas evolutionwas noted during this time. The excess thionyl chloride was then removedby distillation. In a separate 500 ml round bottom flask equipped with aN₂ inlet and a 100 ml addition funel, 27 g (0.14 mol, 100 mol %)2-amino-1-(2- mercapto-2-methylpropylamino)benzene was dissolved in 100ml tetrahydrofuran. Triethylamine (23 ml 0.16 mol, 120 mol %) was thenadded, and the mixture was cooled to 5° C. with an ice-H₂ O bath. Theacid chloride was transferred to the addition funnel and added dropwiseto the amine solution over a period of 2 hours. The mixture was stirredunder N₂ for 18 hours. The solvent was then removed on a rotaryevaporator, and the resulting residual brown oil was diluted with 300 mlethyl acetate. The ethyl acetate was washed sequentially with 100 ml 0.5ml M NaOH and 100 ml 0.5 M HCl. The acid and base layers were bothextracted with an additional 300 ml ethyl acetate. The combined organiclayers were then washed with 100 ml saturated NaCl an drived over 50 ganhydrous sodium sulfate. The sodium sulfate was washed with anadditional 100 ml ethyl acetate. The solvent was removed on the rotaryevaporator to give 52 g (110% yield) of a brown oil which solidifiedupon standing. The crude solid was adsorbed onto 25 g of silica whichwas then placed on a 200-270 g bed of silica and eluted with 2000 ml 20%ethyl acetate/hexane. The appropriate fractions were combined andconcentrated on the rotary evaporator to give 42 g (89% yield) of anorange oil which solidified. This solid was recrystallized from ethylacetate and hexane and decolorized with 3 g activated charcoal. Thesolution was allowed to sit at room temperature for 5 hours, then storedat 0° C. for 18 hours. The resulting beige amorphous solid was collectedon a sintered glass funnel and rinsed with 200 ml hexane. The crystalswere placed in a drying dish and placed in a vacuum desiccator (0.40Torr) for 18 hours. A total of 21.5 g (46% yield) of2-(2-mercapto-2-methylpropylamino)-1-[2-(2-propynylthio-2-methylpropylamido)benzene was obtained.

EXAMPLE 66 2-(2-mercapto-2-methylpropylamino)-1-(2-propynylthio)-2-methylpropylamino]benzene

In a 2000 ml three-neck round bottom flask equipped with a thermometer,a N₂ inlet, and an overhead stirrer, 21.41 g (0.064 mol, 100 mol %)2-(2-mercapto-2-methylpropylamino)-1-[2-propynylthio)-2-methylpropylamide)benzenewas dissolved in 1000 ml anhydrous diethyl ether. The mixture was cooledto -25° C. with a CCl₄ -CO₂ bath. Lithium aluminum hydride (14.50 g,0.38 mol, 600 mol %) was added in three 4.8 g portions over a period of30 minutes. The mixture became viscous and white soon after addition,and then turned green. The mixture was stirred under N₂ for 14 hours,and then an additional 4.84 g (0.127 mol, 200 mol %) LiAlH₄ and 250 mldiethyl ether were added. The mixture was allowed to stir for anadditional 18 hours, then placed in a -20° C. ethylene glycol coolingbath without stirring, for 48 hours. The reaction flask was then placedin a methanol-ice bath and maintained at -10° C. with the periodicaddition of ice. In a 250 ml erlenmyer flask, 27.50 g (0.51 mol)ammonium chloride was dissolved in 100 ml deionized H₂ O. The aqueousammonium chloride solution was then added dropwise to the reactionmixture with stirring over a period of 20 minutes. No gas emission wasnoted after this time, and a white precipitate formed. Hydrochloric acid(500 ml, 0.5 M) and 500 ml, 1.5 M) were added to dissolve the solids.The mixture was transferred to a 4000 ml separatory funnel, andextracted with 3×200 ml diethyl ether. The combined ether layers werewashed with 200 ml saturated NaCl, and dried over 200 g anhydrous sodiumsulfate. The sodium sulfate was washed with an additional 100 ml portionof ethyl acetate. The solvent was removed on the rotary evaporator togive 23.7 g (115% yield) of a gold oil. The crude oil was absorbed ontoa 20 g silica, and placed on 200-270 g bed of silica. The column waswashed with 2000 ml 5% ethyl acetate/hexane. The appropriate fractionswere combined, and concentrated on a rotary evaporator to give twofractions of2-(2-mercapto-2-methylpropylamino)-1-[2-(2-propynylthio)-2-methylpropylamino]-benzeneas product; 7.75 g (38% yield, 91% purity), and 9.25 g (45% yield, 95%purity.

EXAMPLE 672-(2-mercapto-2-methylpropylamino)-1-[2-(2-propynylthio)-2-methylpropylamino]benzenehydrochloride

The HCl salt of each2-(2-mercapto-2-methylpropylamino)-1-[2-(2-propynylthio)-2-methylpropyl-amino]benzenefraction was made by separately dissolving the free amine in 100 mldiethyl ether and cooling the mixture in an ice-H₂ O bath to 5° C.Anhydrous HCl gas was bubbled through the solution for 3 minutes, whichresulted in the precipitation of an amorphous beige solid. The HCl gasand diethyl ether were removed by placing the solution in a 40° C. waterbath, and passing a nitrogen stream over the solution. The first samplewas recrystallized from ethanol and hexane to give 8.5 g (37% yield,98.5% purity) of a crystalline, white solid. The second fractionrequired three successive recrystallizations to obtain a similar purity;6 g (26% yield, 98% purity). A total of 14.5 g (65% yield) of2-(2-mercapto-2-methylpropylamino)-1-[2-(2-propynylthio)-2-methylpropylamino]benzenehydrochloride was obtained.

We claim:
 1. An agent comprising a complex of a radioactive metal with a compound of the formula ##STR21## wherein R₁, R₂, R₃, and R₄ are halogen, hydrogen or lower alkyl containing from 1 to 7 carbon atoms, with at least one of R₃ and R₄ being hydrogen; and one of R₅ and R₅ ' being hydrogen whereas the other of said R₅ and R₅ ' being alkyl containing from 1 to 10 carbon atoms, alkenyl containing from 2 to 10 carbon atoms, alkynyl containing from 2 to 10 carbon atoms or lower alkylcycloloweralkyl containing from 4 to 13 carbon atoms; or with a salt thereof.
 2. The agent of claim 1 wherein said radioactive metal is technetium 99m.
 3. The agent of claim 2 wherein R₅ is hydrogen and R₅ ' is lower alkyl containing from 1 to 7 carbon atoms.
 4. The agent of claim 3 wherein R₅ ' is ##STR22## wherein R₆ is hydrogen or methyl and n is an integer of from 0 to
 5. 5. The agent of claim 4 wherein R₁, R₂, R₃ and R₄ are hydrogen.
 6. The agent of claim 5 wherein said agent is Tc-99m complex of 2-(2-mercapto-2-methylpropylamino)-1-[2-propylthio-2-methylpropylamino]benzene.
 7. The agent of claim 5 wherein said agent is Tc-99m complex of 2-(2-butylthio-2-methylpropylamino)-1-(2-mercapto-2-methylpropylamino)benzene.
 8. The agent of claim 5 wherein said agent is Tc-99m complex of 1-[2-methylthio-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene.
 9. The agent of claim 5 wherein R₆ is methyl.
 10. The agent of claim 9 wherein said compound is Tc-99m complex of 2-(2- mercapto-2-methylpropylamino)-1-[2-(1-methylethylthio)-2-methylpropylamino]-benzene.
 11. The agent of claim 9 wherein said compound is Tc-99m complex of 1-(2-mercapto-2-methylpropylamino)-2-(2-(1-methylpropylthio)-2-methylpropylamino) benzene.
 12. The agent of claim 3 wherein R₄ is methyl and R₁, R₂ and R₃ are hydrogen.
 13. The agent of claim 12 wherein said compound is Tc-99m complex of 2-(2-butylthio)-2-methylpropylamino)-1-(2-mercapto-2-methylpropylamino)benzene.
 14. The agent of claim 2 wherein R₅ is alkenyl.
 15. The agent of claim 14 wherein R₅ ' is ##STR23## wherein R₆ and R₇ are individually hydrogen or methyl, x is an integer of from 0 to 3, is an integer from 0 to 2 and z is an integer of from 0 to
 1. 16. The agent of claim 14 wherein R₁, R₂, R₃ and R₄ are hydrogen.
 17. The agent of claim 16 wherein y is an integer from 1 to
 2. 18. The agent of claim 17 wherein said compound is Tc-99m complex of 1[2-trans-2-butenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino) benzene.
 19. The agent of claim 14 wherein y is
 0. 20. The agent of claim 19 wherein said agent is Tc-99m complex of 2-(2-mercapto-2-methylpropylamino)-1-[2-(4-pentenylthio)-2-methylpropylamino]-benzene.
 21. The agent of claim 19 wherein aid compound is Tc-99m complex of 1-[2-(2-methyl-2-propenylthio)-2-methylpropylamino]-2-(2-mercapto-2-methylpropylamino)benzene.
 22. The agent of claim 19 wherein said compound is Tc-99m complex of 1-(2-allylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene.
 23. The agent of claim 19 wherein said compound is Tc-99m complex of 1-[2-(3-butenylthio)-2-methylpropylamino-2-(2-mercapto-2-methylpropylamino)benzene.
 24. The agent of claim 19 wherein said compound is Tc-99m complex of 1-(2-vinylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene.
 25. The agent of claim 2 wherein R₅ is hydrogen and R₅ ' is alkynyl.
 26. The agent of claim 25 wherein R₅ ' is ##STR24## wherein R₆ is hydrogen or methyl, x is an integer from 0 to 3 and y is an integer from 0 to
 2. 27. The agent of claim 26 wherein R₁, R₂, R₃ and R₄ are hydrogen.
 28. The agent of claim 27 wherein y is
 0. 29. The agent of claim 28 wherein said compound is a Tc-99m complex of 2-(2-mercapto-2-methylpropylamino)-1-[2-(2-propynylthio)-2-methylpropylamino]-benzene.
 30. The agent of claim 2 wherein R₅ ' is loweralkylcycloalkyl containing from 4 to 13 carbon atoms.
 31. The agent of claim 30 wherein R₅ ' is ##STR25## wherein n is an integer of from 0 to 5; p is an integer from 0 to 3 and R₆ is hydrogen or methyl.
 32. The agent of claim 31 wherein R₁, R₂, R₃ and R₄ are hydrogen.
 33. The agent of claim 32 wherein said compound is Tc-99m complex of 1-(2-cyclopropylmethylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene.
 34. A method of imaging organs of the body comprising intravenously injecting into a patient an effective amount of a complex of a radioactive metal with a compound of the formula: ##STR26## wherein R₁, R₂, R₃ and R₄ are halogen, hydrogen or lower alkyl containing from 1 to 7 carbon atoms with at least one of R₃ and R₄ being hydrogen; and one of R₅ and R₅ ' being hydrogen whereas the other of said R₅ and R₅ ' being alkyl containing from 1 to 8 carbon atoms, alkenyl containing from 2 to 10 carbon atoms, alkynyl containing from 2 to 10 carbon atoms or lower alkylcycloloweralkyl containing from 4 to 13 carbon atoms; or with a salt thereof, said complex being injected in a carrier suitable for intravenous injection and scanning the organ to be imaged with scintiscanning means.
 35. The method of claim 34 wherein said radioactive metal is technetium 99m.
 36. The method of claim 35 wherein the organ to be imaged is the brain.
 37. The process of claim 36 wherein R₅ ' is ##STR27## wherein R₆ is hydrogen or methyl and n is an integer of from 0 to
 5. 38. The process of claim 36 wherein said complex is Tc-99m complex of 2-(2-mercapto-2-methylpropylamino)-1-(2-propylthio-2-methylpropylamino)benzene.
 39. The process of claim 36 wherein said complex is Tc-99m complex of 2-(2-butylthio-2-methylpropylamino)-1-(2-mercapto-2-methylpropylamino)-3-methylbenzene.
 40. The process of claim 36 wherein R₅ ' is ##STR28## wherein R₆ and R₇ are individually hydrogen or methyl, x is an integer of from 0 to 3, y is an integer from 0 to 2 and z is an integer of from 0 to
 1. 41. The process of claim 40 wherein said complex is Tc-99m complex of 2-(2-mercapto-2-methylpropylamino)-1-[2-4-pentenylthio)-2-methylpropylamino]benzene.
 42. The process of claim 40 wherein said complex is Tc-99m complex of 1-(2-allylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)benzene.
 43. The process of claim 40 wherein said complex is Tc-99m complex of 1-[2-(3-butenylthio)-2-methylpropylamino-2-(2-mercapto-2-methylpropylamino)benzene.
 44. The process of claim 36 wherein R₅ is hydrogen and R₅ ' is alkynyl.
 45. The process of claim 44 wherein R₅ ' is ##STR29## ##STR30## wherein R₆ is hydrogen or methyl, x is an integer from 0 to 3 and y is an integer from 0 to
 2. 46. The process of claim 45 wherein said compound is Tc-99m complex of 2-(2-mercapto-2-methylpropylamino)1-[2-(2-propynylthio)-2-methylpropylamino]benzene.
 47. The process of claim 36 wherein R₅ ' is loweralkylcycloalkyl containing from 4 to 13 carbon atoms.
 48. The process of claim 47 wherein R₅ ' is ##STR31## wherein n is an integer of from 0 to 5; p is an integer from 0 to 3 and R₆ is hydrogen or methyl.
 49. The process of claim 47 wherein said compound is Tc-99m complex of 1-(2-cyclopropylmethylthio-2-methylpropylamino)-2-(2-mercapto-2-methylpropylamino)-benzene. 